Underfoot foot warmer



Feb. 12, 1957 N 2,781,439

UNDERFOOT FOOT WARMER Filed Sept. 2, 1953 IN VEN TOR. @0141! s I). 11m? United States Patent C T UNDERFOOT FOOT WARMER Thomas D. Lane, San Jose, Calif.

Application September 2, 1953, Serial No.'377,993

3 Claims. (Cl. 219-19) The present invention relates to a foot warmer, and pertains more particularly to a portable foot warmer which may be used under foot, on the floors of buildings such as ofiices, stores, factories or homes.

It is a matter of common knowledge that in cold weather even in the same room, some employees will be too warm, while others will complain of being too cold. This is a problem which is incapable of solution by ordinary heating systems, since it is a matter of individual reaction. Some people prefer a warmer room while others are more comfortable in cooler rooms. Furthermore, many people suffer from poor circulation in the feet and legs. This may be due in part to the sedentary habits which have been acquired by a large number of people, particularly office, store and factory employees.

As a result, the feet of such people frequently are cold in rooms which are otherwise adequately heated.

Some attempts have been made in the past to provide individual foot warmers for use underfoot, but most of such prior heaters are not adequately insulated so as to protect the floor from overheating when placed thereon, and some do not protect against overheating of the feet, with the result that they frequently cause chilblain and other discomforting effects.

An object of the present invention is to make an improved foot warmer. Another object is to make an electrically energized foot warmer with adequate control and one which will not overheat the feet of the user. Another object is to make a simple and inexpensive foot warmer of attractive appearance and long life. Another object is to make a strong, rigid, well insulated, easily fabricated portable electric foot warmer. These and other objects and advantages of the invention are brought out in the following description and the accompanying drawings, wherein:

Fig. 1 is a perspective view of the heater in use beneath an office desk.

Fig. 2 is a plan view of the heater shown in Fig. 1, portions thereof being broken away and a heating ele ment being shown in broken lines.

Fig. 3 is an enlarged fragmentary sectional view taken along line 33 of Fig. 2.

Fig. 4 is a similarly enlarged fragmentary sectional view showing a modified form of construction.

Fig. 5 is a sectional view of a further modified form of the invention.

In the embodiment of the invention shown in Figs. 1 to 3, inclusive, a foot warmer A comprises a base which may be of plywood of suitable thickness, for example A recess 11 is provided in the upper side of the base 10 of a size to receive a heating pad 12 flush therein.

The heating pad 12 is of a well known type consisting of a body 13 which may be of felt, glass-fibre, cloth or other suitable electrically insulative material, having a heating element 14 consisting of a pair of serpentine lengths of electrical resistance heating element wire 14a and 14b embedded therein. Such wire, as is well known to those versed in the art, may be of suitable nickel and 2,781,439 Patented Feb. 12, 1951 chromium alloy or other metal or alloy of suitable electrical resistance, and having required heat and corrosion resistant qualities. The resistance wire 14a and 14b are wrapped with asbestos or glass fibre insulation also in a manner well known to those familiar with the ant of heating pads.

A pair of conventional thermostats 15, 15 are provided at suitable intervals in the heating element 14 and preferably are buried, partly in recesse 17 (Fig. 3) provided therefor in the base 10 and partly in recesses 18 in the pad 12. If .the thermostats 15, 15 are of small size the recesses 17 in the base 10 may be omitted since the reoesses 18 in the material of the pad 11 will be sufiicient to embed the thermostats substantially flush therein.

A layer 19 of suitable reflective sheet insulating material such as aluminum foil preferably is placed to cover the bottom of the recess 11 beneath the heating pad 12 to reflect radiant heat from the element 14 upwardly. A second layer 20 of rather heavy aluminum foil, or light gauge tin plate steel of the type from which tin cans are made, is provided to overlie the heating pad 12. This top foil layer 20 preferably extends as a waterproof shield throughout the entire top surface area of the base member 10, and preferably is coated with a dull black paint on it under side throughout the area thereof over the heating pad 12 to facilitate the absorption, and reradiation from its upper surface, of radiant heat from the element 14. A layer 21 of wear-resistant material such as a good grade of carpet is provided over the entire upper area of the base member 10, and substantially coextensive therewith. This layer 21 of wear resistant material is secured marginally to the base 10 by tacks or staples 22 which may be applied with a conventional type of stapler, not shown.

A frame of channel edging material 23 of suitable material, such as stainless steel, then is mounted marginally around the entire base (Fig. 1). This channel edging material grips the wear resistant material 21 firmly to the base and provides a neat and long wearing trim entirely around the device. The corners 23a of the channel edging material 23 are mitred in a usual manner to provide neat, tight fitting corners; the trim channel 23 is secured against displacement by small nails 23b driven through the bottom flange 24 of the trim channel 23 and into the base It).

A usual three-wire lead cord 27 extends from the heat-- ing element 14 along a groove 29 provided therefor in the base 10 and through an insulating grommet 28 which is inserted in the outer end of the groove 29 through a hole (not shown) provided therefor in the edging member 23. An insulated staple 30 spans the cord 27 and is driven into the base It to anchor the cord against pulling stresses in the event a user should employ the cord 27 as a handle for moving the device.

\ A three stage switch 31 of a conventional type is provided at the outer end of the three wire cord 27 and a length of usual two conductor cord 32 is connected to the outer side of the switch 31. A conventional wall plug 33 is mounted on the outer end of the cord 32 for plugging into a wall receptacle of a usual type connected to an electrical circuit of desired voltage, for example, the usual volt house lighting circuit.

The switch 31 is so connected that one conductor 32 of the two-conductor cord 32 is connected at all times through a conductor 27a of the cord 27 and through a conductor 15a (shown in broken lines in Fig. 2) to the terminal end of the resistance element 14. The thermostats 15, 15 are connected in series in the conductor 15a.

The heating element 14 consists of two resistance wires 14a, shown in dash-dot lines in Fig. 2, and a shorter resistance wire 14b shown in dash-two-dot lines in Fig. 2.

ductor 32b of the two-wire cord 32, is connected through a conductor 27b of the three wirecord 27, and through the shorter resistance wire 14b to the terminal end of the thermostat conductor 15a. In the medium heat position of the switch 31, the conductor 32b of the two conductor cord- 32 is connected through a conductor 27c of the three conductor cord 27 to the longer resistance wire 14a and thence to the terminal end of the thermostat wire 1511. In the low heat position. of the switch the conductor 32b is connected to the conductors 27B and 27C in parallel, and thence through the resistance element wires 14a and 14b to the terminal end of the thermostat Wire 1511.

The heatingelement 14 preferably is approximately a 60 to 100 watt unit and a suitable size for the pad 12 is approximately 10 x 12". A suitable size for the base plate 10 is approximately 18" x 2-7. This provides a heater which is readily insertable under most desks and tables, and also is a convenient size for use to stand upon, for example, behind a counter in stores, or in factories, filling stations or other places where the device may be of use.

A modified form of the invention is shown in Fig. 4. It is similar to that shown in Figs. 1, 2 and 3, with the exception that a sheet 34 of corrugated cardboard of suitable strength and approximately in thickness is provided beneath the heating pad 2. With this construction of Fig. 4, the pad receiving recess 11 is deepened as required to accommodate the additional thickness of the corrugated member 34. This underlying layer of corrugated cardboard provides additional air cell insulation between the element 14 and the floor upon which the device may be placed which still further protects the floor from possible heat damage. The resilient heating pad- 12 overlying the corrugated sheet 34 cushions the load of a person standing on the device, so that corrugated cardboard of the type commonly used for the making of shipping cartons has been found suitable for making the member 34. A layer 21 of carpet may be provided over the entire top area of the assembled parts, the same as in Figs. 1 to 3, inclusive.

A further modification of the invention is shown in Fig. wherein a base member a, of suitable rigid insulative material such as plywood, has no recess therein to receive the pad 12, and the pad 12 is laid on top of the base 10a and is secured thereto as by staples 38 driven marginally through the pad beyond the heating element 14 therein, and into the base. Suitable material such as corrugated cardboard 39 of apportionat'ely the same thickness as the pad 12 is mounted to cover the entire surface area of the base 10a beyond the pad 12 and is secured to the base as by staples 40. This arrangement provides a flush, substantially continuous top surface for supporting a top wear resistant member 35.

For use in factories, filling stations and stores, where the device is to be used by persons standing upon it, and where appearance is not a major factor, the wear resistant top member may consist of a sheet 35, of hard pressed wooden composition board of the type known to the trade as Masonite, or a sheet of suitable wear resistant plastic sheet material. Such materials may be easily cleaned when soiled by mud or grease, and, being electrically nonconductive are more satisfactory than carpet in locations where they are apt to be used by persons having wet or soiled shoes.

A marginal frame 23 of channel edging material may be applied around the device shown in Fig. 5 in the same manner as that described previously herein for the construction shown in Figs. 1 to 3, inclusive.

The transfer of heat from the pad 12 to ones feet resting on the device is principally by direct conduction through the carpet 21, although there is some heat transfer by radiation and a minute amount by convection. Therefore, evenwhen ones shoes are wet, in a very short time the feet become warm, and this results in a general feeling of warmth and comfort all over ones body.

No noticeable amount of heat is transferred by the present device to the ambient air, so that the air one breathes is not heated by the device as it is with some types of spot heaters. Since the amount of moisture a unit quantity of air will carry increases with the air temperature, a certain coolness in the air one breathes reduces its tendency to dry out the mucous membranes of the nose and throat, whichadds to the sense of comfort experienced, providing the body itself is sufficiently warm.

After one has used the device a few times, it has been noted that ones feet will shift, as soon as they are comfortably warmed, from the heated central area toward the marginal zones of lesser heat. This has been observed to be without intention or even knowledge on the part of the person using the device. The marginal area of the device surrounding the pad 12 provides a zone which, even though not substantially heated, provides insulation in the event the floor beneath is cold. Thus, the device may be left turned on at all times during cold or inclement weather, and the feet will tend to find their own comfort zone thereon, while the temperature of the ambient air is not noticeably affected.

The device comprises a simple, compact, easily fabricated foot warmer with a wide variety of applications and one which requires no more electrical current to operate than a medium size incandescent lamp bulb.

While i have illustrated and described a preferred embodiment of the present invention, it will be understood however, that various changes and modifications may be made in the details thereof without departing from the spirit and scope of the invention as set forth in the appended claims.

I cIaim:

1. A foot warmer for under-foot use comprising a rigid base plate of poor thermal conductivity having a recess in the upper side thereof, a heater pad fiush-mounted in said recess, said heater pad comprising a flexible body, a heating element arranged in said pad body, thermostat control means connected to said heating element to limit the maximum temperature thereof, a conductor cord connected to said heating element for connecting said element to a source of electrical energy, a thin sheet of heat conductive waterproof material overlying said pad and extending onto said base marginally around the recess therein, a layer of wear resistant material mounted over the entire top area of said base to enclose said pad in said'recess, and fasteningmeans securing said wear resistant material marginally to said base.

2". A foot warmer for under-foot use comprising a rigid base plate, cushioning material mounted on the top surface of said: base plate and substantially co-extensive therewith, an electrical resistance heating element arranged in serpentine fashion throughout a central area of said cushioning means, thermostat control means connected to said heating element to limit the maximum temperature thereof, a conductor cord connected to said heating element for connecting said element to a source of electrical energy, switch means mounted to control the flow of electrical current through said element, a layer of wear resistant material overlying the top area of said base and substantially co-extensive therewith, and a frame of metal. channel. binding material fitted to receive and enclose the marginal portions of said base plate and said wear resistant material therein, thereby to grip the wear resistant material to the base and to strengthen and prote'ct said base and said wear resistant material.

3. A foot warmer for under-foot use comprising a rigid base plate of poor thermal conductivity and of substantial thickness having a recess in the upper side thereof, a heater pad flush-mounted in said recess, said heater pad comprising a flexible body, a heating element arranged in said pad body, thermostat control means connected to said heating element to limitthe maximum temperature thereof, a conductor cord connected to said heating element and flush mounted in a groove provided therefor in the base plate, for connecting said element to a source of electrical energy, a thin sheet of heat conductive waterproof material overlying said paid and extending onto said base marginally around the recess therein, a layer of wear resistant material mounted over the entire top area of said base plate to enclose said pad in said recess, whereby heat is conducted from the heating element through the pad, the sheet of waterproof material and the wear resistant material for heating by conduction shoes and feet placed thereon, the element being insulated by the base plate from a floor therebeneath, and fastening means securing said wear resistant material marginally to said base.

References Cited in the file of this patent UNITED STATES PATENTS Hicks Mar. 5, 1929 Gardner Mar. 29, 1938 Baylis Aug. 30, 1938 Howard et al Sept. 17, 1940 Roberson June 13, 1950 Morris July 4, 1950 Vogel Mar. 6, 1951 Callender Mar. 20, 1951 McCann Sept. 30, 1952 Pontiere Nov. 25, 1952 

